During implementation of interconnection between an IP multimedia subsystem (IP Multimedia Subsystem, IMS) network and a conventional circuit switched (Circuit Switched, CS) network, a media gateway control function (Media Gateway Control Function, MGCF) entity is required to implement mutual conversion between Session Initiation Protocol (Session Initiation Protocol, SIP) signaling and Integrated Services Digital Network User Part (Integrated Services Digital Network User Part, ISUP)/Bearer Independent Call Control (Bearer Independent Call Control, BICC) signaling.
In the prior art, in a CS network, a call reference parameter or a global call reference parameter may be used to identify a call, and the parameter may also be used to perform charging for the call; in an IMS network, a call identifier Call-ID parameter may be used to identify a call, and an icid parameter is used to perform charging for the call. However, a disadvantage of the prior art is that when a cross-domain call is made, cross-domain call association cannot be implemented because a parameter used to identify a call in the CS network is inconsistent with that used in the IMS network. In an actual application, because charging cannot be performed by using a unified call identifier, charging for a call becomes complex.